My current DA is 32. I am focusing on content quality of my web page and make sure every page does have a high-quality content with good internal linking structure. As we all know, Content is a King and Google also gives first priority to quality content.

DA/PA is highly effected by link building. I would also make sure you check your citation flow/trust flow with majestic too. Your links need to be high quality high DA sites as well. A bunch of 5DA low TF/CF sites won't get you anywhere.

If you want to increase your website DA, then you should have to follow some important techniques such as post your content in the form of articles, blog, guest posting on high DA sites on regular basis. Make sure you are not doing overlinking because it might harm your website.

DA or Domain authority is the measure of strength and popularity of your domain in search engines. It is measured by Moz and your domain is ranked between 0 to100 depending on the popularity and trust. DA can be improved by good content update and also by building backlinks from other relevant domains.

Yes,white hat seo technique is always good to increase DA.If we want to make long term investment in our website then this technique will be good for us to increase DA.For increasing DA we should use white hat techniques that includes following stuff:1)good and original content2)perfect keywords , titles , meta tags etc.3)quality inbound links4)building backlinks etchope you are clear with this ans find more on how white hat techniques useful here http://crbtech.in/SEO/white-hat-seo/ i have found.